Stability constants of complexes of metals with humic and fulvic acids under non‐acid‐conditions

Abstract

Abstract Stability constants of complexes of four divalent metal ions viz. Cu 2+ , Zn 2+ , Mn 2+ and Ca 2+ with humic (HA) and fulvic acids (FA) at pH values of 7 and 8 were determined. The log K (logarithm of the stability constant) ranged from 3.09 to 7.77 and from 2.22 to 5.98 for metal‐humic and metal fulvic acid complexes, respectively. Sequentially, the order of stability constants were as follows: Cu> Ca> Mn> Zn and Cu> Ca> Zn> Mn for metal ‐HA and metal‐FA complexes, respectively, indicating a higher degree of complexation with Cu metal ion.